It increasingly appears Barack Obama will name Joe Biden as his running mate. (Getty Images)

(CNN) - As his major competitors slipped out of contention late Friday night, Senator Joe Biden of Delaware emerged as the top remaining contender for the Democratic vice presidential nomination.

Virginia Governor Tim Kaine, Indiana Senator Evan Bayh of Indiana and Senator Hillary Clinton of New York - presumptive nominee Barack Obama's main primary season rival – have all been informed that they will not be the Illinois senator's running mate, sources tell CNN.

Neither Biden – a 1988 presidential candidate – nor Obama's campaign has commented on whether or not he has been asked to join the Democratic ticket. An official announcement of Obama's final pick is expected within hours.

(CNN) - A source close to Evan Bayh expressed disappointment with the decision. "We are all sad," the source tells CNN. "But Evan was cool with this, whatever happened. He understands what he's got - a family, and a life he's very happy in."

The Indiana senator, son of 1976 presidential candidate Senator Birch Bayh, has been a perennial VP contender.

Sources close to Governor Tim Kaine of Virginia says he has been informed he will not be Obama’s Vice President. One source tells CNN that Obama personally made the call to Governor Kaine. Another source tells CNN that Kaine left Richmond for Denver a few hours ago, and has now arrived in Denver for the convention.

(CNN) - Two prominent Democrats close to Hillary Clinton expressed frustration Friday over a report Barack Obama’s campaign never formally vetted the New York senator for the vice presidential spot, and predicted the revelation could further rile some of her most fierce supporters just as the party is set to kick of its national convention in Denver.

Longtime Clinton loyalists Paul Begala and James Carville, who have endorsed Obama's White House bid, told CNN’s Wolf Blitzer Friday a Politico report claiming the Obama campaign did not officially consider Clinton for the coveted position would likely further anger some Democrats already wary of the Illinois senator. Both Carville and Begala are CNN contributors.

The matter is even made worse, Begala said, by the fact that Obama himself suggested to reporters earlier in the summer that he would consider Clinton, saying his one-time rival would be on "anybody's shortlist."

"There's two camps in Hillary land - there's the peacemakers and the PUMAs - Party Unity My Aunt Fannie," Begala said. "They're still not behind Obama. Some of them are stirring up a lot of trouble. I don't like it. I'm a peace maker. This story empowers the PUMA crowd because they see this, and I do too, as sort of disrespecting Senator Clinton and breaking Senator Obama's word.

"It's the one glitch in a beautiful process," Begala also said.

Carville, who along with Begala donated the maximum allowable amount to Obama's campaign immediately after Clinton exited the race, expressed particular frustration over reports Obama had not asked Clinton about her thoughts on who should fill the vice presidential slot on the ticket.

"I think we suffered a big blow today to the hard-liners," he said. "I don't think he's spoken to Senator Clinton about the vice presidency or even sought her counsel."

"We may be surprised if he picks her, but after that, it was pretty clear that not only were they not interested in had having her, they were not interested in her opinion," he added.

But former Clinton lawyer Greg Craig, who has supported Obama this election cycle, suggested Friday Clinton did not need to be formally vetted by the Obama campaign because of her lengthy stint in the public eye.

“I think that Senator Clinton is well known," he said. "Her service is well known. Her record is well known. And she herself said to the world that she's been vetted and ready to serve."

Meanwhile, appearing at the New York State Fair Friday, Clinton said she has never been interested in being Obama’s vice president.

I never said I [wanted the job],” she told reporters. “I have always said I will do whatever I can because I feel so strongly in making sure that we elect Senator Obama our next president.”

Since declaring the Democratic vice presidential pick would first be announced over e-mail and text message, several hoax announcements of the Illinois senator's choice have circulated, purporting to be from the Obama campaign.

The latest came in e-mail Friday morning that hit the inboxes of many White House reporters, carrying the subject, "My Vice President."

The e-mail, from the address obama08campaign@aol.com, was purportedly from Barack Obama and read, "I said you would be the first to know, and you are - I have selected Virginia Gov. Tim Kaine as my running mate!”